Point out the error in the program

#include<stdio.h>
int main

Point out the error in the program

#include<stdio.h>
int main()
 {
     int a=10;
     void f();
     a = f();
     printf("%d\n", a);
     return 0;
 }
 void f()
 {
     printf("Hi");
 }

2) What will be the output of the program?

#include<stdio.h>
int sumdig(int);
int main()
{
     int a, b;
     a = sumdig(123);
     b = sumdig(123);
     printf("%d, %d\n", a, b);
     return 0;
 }
int sumdig(int n)
 {
     int s, d;
     if(n!=0)
     {
         d = n%10;
         n = n/10;
         s = d+sumdig(n);
     }
     else
         return 0;
     return s;
 }

3) Point out the error in the program

#include<stdio.h>
int main()
 {
     int a=10;
     void f();
     a = f();
     printf("%d\n", a);
     return 0;
 }
 void f()
 {
     printf("Hi");
 }

4) How many times the program will print "Study 2 Online" ?

  #include<stdio.h>
  int main()
 {
     printf("Study 2 Online");
     main();
     return 0;
 }

5) What will be the output of the program?

#include<stdio.h>
int fun(int, int);
 typedef int (*pf) (int, int);
 int proc(pf, int, int);
int main()
 {
     printf("%d\n", proc(fun, 6, 6));
     return 0;
 }
 int fun(int a, int b)
 {
    return (a==b);
 }
int proc(pf p, int a, int b)
 {
    return ((*p)(a, b));
 }